i don't have access to the server right now, and mine are hacmp 6, so menu must be different but normally

1.)
i go to smith hacmp, extended configuration, storage, filesystems and change it from there, i gave you the menu options by memory so they might be a little different.

2.)

Extended sincronization and verification shold show you that and give the option to correct it.
If that doesn't work and space allow it, i would reduce de fs with chfs in the active node to the original size, and perform nr.1

We are taking chfs command to increase the F/S time stamp is not update on
Passive node (we have to manual update of that)
So should be take cluster C-SPOC menu use to increase F/S
Because /etc/cluster/bin/etc/objrepos global ODM of cluster. will time
stamp updated on all cluster environment.

If it is just FS extension. Then its perfectly fine if you extended it on
primary node. During failover HACMP will do a Lazy Update of VG on failover
node and updates will be reflected on failover node.

In 7.1 we have enhanced concurrent volume group by default. So if you have
EC VG configured in fast disk takeover config. As soon as you run chfs
command to extend filesystem the changes will be applicable immediately on
secondary node. In case you are creating a new FS you should use CSPOC.

Procedure 2 mentioned by you its absolutely correct. But during failover
hacmp takes care of it on its own in case there is a difference between
time stamp of ODM and VGDA on secondary node. So you don't need to do it
manually.

Procedure 1 can cause an outage as you are exporting and importing the VG
again. It will change auto varyon of VG to yes. And it will try to vary on
the VG on node 2 while its still active on node 1.

With PowerHA 7.1 its best to use Enhanced concurrent VGs with fast disk
takeover. So any changes done in VG will propagate to both the nodes in
cluster and there is least possibility of VGs getting out of sync on nodes
in a cluster.